Add a method to ContentEntityBase for getting its Bundle entity

So turns out EntityTest has the bundle key, but doesn't technically have bundles. The current code errors out when an entity type doesn't have a bundle key (e.g User). Ideally we remove the key from EntityTest but that may have cascading effects that would balloon this issue. I'm also not keen to add EntityTestWithoutBundle because that is what EntityTest is supposed to be... 🤔

EntityTest is magic, it uses EntityTestHelper to define bundles on the fly. I'll open an issue to document that on the entity class.

I checked, and accessing ->entity on a field that's a string rather than an entity ref works ok, but it feels ugly to be relying on that and accessing a property we know might not exist. So it's better with the guard as it is now.

This is good to go now.

Thanks!

Left a recommendation on the MR for adding an extra guard to ensure the field is of the correct type. Fine to self RTBC after that change.

@acbramley pointed out that this is already covered by \Drupal\Core\Entity\ContentEntityBase::baseFieldDefinitions

Credits

larowlan → closed merge request !12451

Committed to 11.x - thanks!